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BB10004- Biochemistry 2 > Lecture 6- Fatty acid biosynthesis > Flashcards

Lecture 6- Fatty acid biosynthesis Flashcards

(58 cards)

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1
Q

3 Functions of complex lipids

A
  • Triacylglycerols (store)
  • Principle components of cell walls (phospholipid bilayer)
  • Cell signalling
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2
Q

Different between breakdown and biosynthesis of fatty acids?

A

Breakdown- releases energy

synthesis- requires energy, and reducing equivalents

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3
Q

How much fatty acids turned over per 24 hours? this accounts for?

A

200g

8% of the body basal 02 consumption

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4
Q

Major biosynthetic product of fatty acid synthesis is?

A

Palmitic acid:

C16:0 CH3(CH2)14COOH

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5
Q

Most naturally occurring fatty acids have

A

even numbers of carbons

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6
Q

Fatty acids biosynthesis adds?

A

2 carbon units at a time

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7
Q

comparison between fatty acid synthesis and breakdown?

A

Synthesis:Cytoplasmic
NADP+/NADPH
CO2 required as HCO3-

Breakdown: Mitochondrial
NAD+/NADH
No CO2 required

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8
Q

What is the experimental evidence that synthesis occurs in the cytosol?

A

1) Homogenize tissue (eg blender)
2) Centrifuge @100 000g
3) Forms:
Pellet: nuclear material, mitochondrial fragments and membranous debris

Soluble fraction: no membrane fractions, only double proteins

4) With the soluble fraction, protein precipitation using a salt (ammonium sulphate).

Forming 8 soluble fractions. None supported biosynthesis on its own, needs to be combined with another. One in which contains the cofactor biotin

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9
Q

Describe stage one of fatty acid biosynthesis?

requires?

forms?

A

ACTIVATION: Carboxylation of acetyl-CoA forming Malonyl CoA and water as a by product

requires biotin and ATP hydrolysis

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10
Q

Enzyme requires in the first stage of fatty acid biosynthesis? Characteristic ?

A

Acetyl- CoA carboxylase

Closed related to pyruvate carboxylase

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11
Q

First step is what type of reaction (not activation but ?..)

A

Irreversible

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12
Q

How many step reaction (1st step of fatty acid biosynthesis)

A

2 step

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13
Q

Two enzyme domains in which make up Acetyl-CoA carboxylase? Function of each>

A

Biotin carboxylase ( carboxylation of biotin) and transcacrboxylase (transfer of the carboxyl group to acetyl-CoA to form malonyl-CoA)

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14
Q

Enzyme structure of Acetyl-CoA carboxylase in pros and eus

A

pros: 3 protein complexes in separate domains (multiple genes within an operon)
eu: single gene, codes for a single large protein

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15
Q

Step 2 of fatty acid biosynthesis?- general name?

A

chain elongation

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16
Q

Enzyme which controls stage two of fatty acid biosynthesis?

A

Fatty acid synthetase

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17
Q

Products and reactants (not relative) of step two fatty acid biosynthesis

A

reactants: acyl- coa, malonyl-CoA, NADPH and H+ ions
products: forms a c-c bond between malanyl units and acetyl CoA. CO2. NADP+ CoA and h20

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18
Q

How many malonyl- coA subunits are required in step two of fatty acid biosynthesis?

A

7

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19
Q

How many NADPH subunits are required in step two of fatty acid biosynthesis?

A

14

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20
Q

How many H+ subunits are required in step two of fatty acid biosynthesis?

A

14

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21
Q

How many CO2 units are formed (step two of fatty acid synthesis)?

A

7

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22
Q

How many NADP+ units are formed (step two of fatty acid synthesis)?

A

14

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23
Q

How many CoA subunits are formed in stage two of fatty acid biosynthesis?

A

8

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24
Q

How many h20 units are formed (step two of fatty acid synthesis)?

25
Function of acetyl CoA in step two of fatty acid biosynthesis ?
primes the reaction and becomes the methyl terminus of the fatty acid chain
26
Malonyl CoA provides how many carbons in order to extend the fatty acid chain chain
2 carbons (hence why you need 7 in order to form palmitate)
27
Acetyl CoA provides how many carbons to the fatty acid chain?
2
28
Overall reaction equation
8 acetyl-CoA +7 ATP +14NADPH +14H+ > PAL +8CoA +6 h20 +ADP +7Pi +14NADP+ two equations added together, causes malonyl-coa intermediate to be cancelled out
29
Fatty acid synthase catalyses how many reactions and therefore?
7 | requires an active site for each reaction
30
Where is Fatty acid synthase found in cells?
cytosolic fraction of cells
31
What does Fatty acid synthase require?
requires malonyl-CoA & acetyl-CoA, NADPH (cofactor)
32
Is Fatty acid synthase soluble or insoluble and why?
relatively insoluble as it is synthesising insoluble fatty acids
33
Can we detect the intermediates in solution of a reaction being catalysed by fatty acid synthase?
no free unbound intermediates
34
Prosthetic group required by fatty acid synthase
4 phosphopantetheine
35
difference in Fatty acid synthase structure (polypeptide) in bacteria, yeast and eu's?
Bacteria, 8 separate genes within an operon, 1:1 ratio to form a protein complex with 8 domains Yeast- few chains Eu- single polypeptide (large)
36
ACP function and what it stands for
Acetyl carrier protein | Carrier protein in which becomes attached to acetyl-CoA
37
Enzyme which allows the attachment of ACP to acetyl CoA
Acetyl transacylase
38
First step in the second stage of fatty acid synthesis?- equations
Acetyle-CoA> acetyl-ACP +coash (controlled by the enzyme: acetyl transacylase) Acetyl-ACP> Acetyle~ synthase (enz) + ACP-SH synthase domain: B=ketoacyl ACP synthase
39
Second step of the second stage of fatty acid synthase: ENZYME involved?
Malonyl Transacylase
40
Second step of the second stage of fatty acid synthase: what occurs ?
malonyl group is transferred to ACP and CoA also formed
41
Third step of the second stage of fatty acid biosynthesis is what type of reaction
condensation reaction
42
Third step of the second stage of fatty acid biosynthesis is what catalysed by what,
B-ketoacyl-ACP synthase
43
Reaction of the third step of the second stage of fatty acid biosynthesis
Acetyl-synthase+ Malonyl-ACP >> b-ketoacyl-ACP +CO2 _ synthase-SH
44
Purpose of the third step of the second stage of fatty acid biosynthesis
c-c bond formation due to CO2 cleavage
45
General name for the fourth step of the second stage of fatty acid biosynthesis
REDUCTION
46
Enzyme for the fourth step of the second stage of fatty acid biosynthesis
B-ketoacyl ACP reductase
47
cofactor for the fourth step of the second stage of fatty acid biosynthesis
NADPH + H+
48
reaction for the fourth step of the second stage of fatty acid biosynthesis
B-ketoacyl-ACP to form B-hydroxacyl-ACP nadph + h+ needed
49
General name for the 5th step of the second stage of fatty acid biosynthesis??
Dehydration (removal of water to form a double bond)
50
Enzyme for the 5th step of the second stage of fatty acid biosynthesis??
B-hydroxyacyl-ACP dehydrase
51
reaction for the 5th step of the second stage of fatty acid biosynthesis??
B-hydroxyacyl-ACP (water removed) to form aB trans enoyl-ACP
52
General name of the 6th step of the second stage of fatty acid biosynthesis??
REDUCTION
53
Enzyme of the 6th step of the second stage of fatty acid biosynthesis??
Enoyl-ACP reductase
54
Reaction of the 6th step of the second stage of fatty acid biosynthesis??
aB trans enoyl-ACP + NADPH + H+ >>>> Acyl-ACP
55
How is ACP regenerated
This acyl group is then transferred to the β-ketoacyl synthase domain of the protein Freeing the ACP to bind another malonyl group
56
How does the process continue?
With a C4 acyl group attached to the β-ketoacyl synthase domain process repeated
57
Last step of the second stage of fatty acid biosynthesis (REACTION)
palmitoyl-ACP>>>> palmitate + ACP-SH
58
Where is palmitate found in highest quantities ?
in mammalian liver

BB10004- Biochemistry 2 (3 decks)

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